The first record of herpes virus in history dates back to the ancient Greece era before Christ. Herpes virus infrequently develops after primary infection, but hides in ganglia or the like for a long time. When the immune ability of a human is reduced, the virus is activated and proliferates to develop symptoms. In this case, herpes virus targets a wide range of tissues, such as skin, genital organs, eye ball, nerves, and the like. Even though antibodies which neutralize the virus are present in blood, symptoms often appear. It is thus believed that a reduction in cellular immune function is involved in the onset of symptoms.
Examples of herpes virus transmissible to a human include herpes simplex virus (HSV-1), herpes simplex virus (HSV-2), varicella zoster virus (VZV), EB virus (EBV), cytomegalovirus (HCMV), human herpes virus 6 (HHV-6), human herpes virus 7 (HHV-7), human herpes virus 8 (HHV-8), and the like.
HSV-1 causes gingivostomatitis or herpes facialis as a symptom of primary infection, and herpes labialis, herpes keratoconjunctivitis, herpes encephalitis as a symptom of recurrent infection. A major latent infection site of HSV-1 is trigeminal ganglia. HSV-2 causes genital herpes as a symptom of primary infection and genital herpes or neonatal herpes as a symptom of recurrent infection. A major latent infection site of HSV-2 is sacral ganglia. VZV causes chickenpox (varicella) as a symptom of primary infection and chickenpox and herpes zoster as a symptom of recurrent infection. A major latent infection site of VZV is dorsal root ganglion. EBV causes no symptom or causes infectious mononucleosis as a symptom of primary infection and Burkitt's lymphoma, or rhinopharyngeal cancer as a symptom of recurrent infection. A major latent infection site of EBV is B cell. HCMV causes no symptom as a symptom of primary infection and causes pneumonia, cytomegalic inclusion disease or the like as a symptom of recurrent infection. Latent infection sites of HCMV are believed to be macrophage and blood progenitor cells. HHV-6 causes exanthema subitum as a symptom of primary infection and exanthema subitum (pneumonia) as a symptom of recurrent infection. Latent infection sites of HHV-6 are believed to be macrophage and blood progenitor cells. HHV-7 causes exanthema subitum as a symptom of primary infection. A major latent infection site of HHV-7 is T cells. HHV-8 causes no symptom as a symptom of primary infection and causes Kaposi's sarcoma, PEL, and Castleman's disease as a symptom of recurrent infection. A major latent infection site of HHV-8 is B cells. Thus, a variety of infectious diseases are caused by herpes viruses.
An attenuated live vaccine against chickenpox virus is the only successful human herpes virus vaccine (Takahashi M., et al., Lancet, 2:1288, 1974). However, this attenuated live virus was accidentally obtained and is based on the characteristic that chickenpox is more effective to humoral immunity since it causes systemic infection due to viremia, unlike other herpes viruses. Therefore, a vaccine which can be universally utilized for herpes viruses is not yet available.
HSV is a representative herpes virus which is infectious to a human. HSV infection results from inoculation of the virus to mucosa, or the virus invading through a break in the skin. Most primary infections occur in the neonatal periods, but most children with a primary infection quickly improve. HSV is transmitted to a baby from an infected nurser or more generally an infected mother (specifically, a baby encounters genital herpes as the baby passes through the birth canal). In this case, HSV infection causes serious symptoms. For example, disseminated neonatal herpes infection causes hepatitis or the like, so that a baby may die.
Once HSV is acquired in the body, HSV is held in the body over a lifetime. During the latency period, HSV is localized in neurons in sensory ganglia (in the case of facial lesions, trigeminal ganglia are usually involved), and an infected patient is a symptomatic. However, HSV is activated by stimuli, such as menstruation, excessive exposure to sunlight or cold wind, pituitary gland or adrenal gland hormones, allergic reactions, or fever. The activated HSV is replicated and takes over the mechanism of a host cell, producing infectious mature virus particles and causing cell death. Symptoms caused by such a recurrent attack often appear on the mouth, face, and genital organs. For example, keratitis due to recurrent HSV is considered to be a major cause of blindness. Further, HSV infection to genital organs is frequent, and the incidence of sexually transmitted diseases (e.g., genital herpes) caused by HSV is significantly high. More specifically, examples of recurrent HSV-induced diseases which are caused by the recurrent attack include mucocutaneous diseases, such as herpes labialis (a disorder on the lips usually called “fever blister” or “cold sore”), gingivostomatitis (the mouth and gingiva are covered with vesicles and the vesicles rupture to form ulcers), pharyngitis, tonsillitis, keratoconjunctivitis (keratitis or inflammation of the cornea, which progresses to dendriform ulcer and eventually to cicatrization of the cornea, resulting in blindness), and genital herpes. In rare cases, HSV infection causes encephalitis, eczema herpeticum, traumatic herpes, and hepatitis.
Herpes simplex virus 2 (hereinafter also referred to as HSV-2) induces skin mucosa infection in genital organs. After infection, virus is maintained in the sensory ganglia, and then activated to cause recurrent HSV infection (Price, R. W., Walz, M. A., Wohlenberg, C., and Notkins, A. L. (1975) “Latent infection of sensory ganglia with herpes simplex virus: efficacy of immunization”, Science 188, 938-940). Many researchers have extensively studied immune reactions with HSV-2 infection using animal models.
It has been reported that a major antigen-presenting cell (APC) is the dendritic cell (DC), including Langerhans cell (LC), and a number of macrophages (Mφ) and B cells in the vagina (Parr, M. B., and Parr, E. L. (1991), “Langerhans cells and T lymphocyte subsets in the murine vagina and cervix”, Biol. Reprod. 44:491-498; Nandi, D., and Allison, J. P. (1993), “Characterization of neutrophiles and T lymphocytes associated with the murine vaginal epithelium”, Reg. Immunol., 5, 332-338).
It has been reported that T cells play an important role as a cytotoxic T lymphocyte (CTL), and produce antiviral cytokines against HSV-2 infection (Milligan, G. N., and Bernstein, D. I. (1995), “Analysis of herpes simplex virus-specific T cells in the murine female genital tract following genital infection with herpes simplex virus type 2”, Virology 212, 481-489.; Parr, M. B., and Parr, E. L. (1998), “Mucosal immunity to herpes simplex virus type 2 infection in the mouse vagina is impaired by in vivo depletion of T lymphocytes”, J. Virol. 72, 2677-2685; Milligan, G. N., Bernstein, D. I., and Bourne, N. (1998), “T lymphocytes are required for protection of the vaginal mucosae and sensory ganglia of immune mice against reinfection with herpes simplex virus type 2”, J. Immunol. 160, 6093-6100).
It has been reported that mutants lacking replication capability can elicit a wide spectrum of immune reactions (Morrison, L. A., Da Costa, X. J., and Knipe, D. M. (1998), “Influence of mucosal and parenteral immunization with a replication-defective mutant of HSV-2 on immune responses and protection from genital infection”, Virology 243, 178-187: McLean, C. S., Ni Challanain, D., Duncan, I., Boursnell, M. E. G., Jennings, R., and Inglis, S. C. (1996), “Induction of a protective immune response by mucosal vaccination with a DISC HSV-1 vaccine”, Vaccine 14, 987-992).
It is known that infection with attenuated HSV-2 causes the flow of HSV-2-specific T cell type 1 (TH1)-like CD4+ cells into the vagina (Milligan, G. N., Bernstein, D. I., and Bourne, N. (1998), “T lymphocytes are required for protection of the vaginal mucosae and sensory ganglia of immune mice against reinfection with herpes simplex virus type 2”, J. Immunol. 160, 6093-6100).
However, in the pathology of HSV diseases, a detailed relationship between the role of a HSV-specific virus gene and immune reactions has not been fully clarified.
Thus, under the present circumstances, there is no decisive method for preventing or treating diseases or disorders caused by herpes viruses.
As a cancer therapy, there are generally surgical excision, chemotherapy, radiation therapy, and the like at present. However, none of these therapies have a sufficient effect on some types of cancers. For example, in the case of progressive pancreatic cancer and progressive ovarian cancer, a favorable prognosis is not obtained. Particularly, when progressive pancreatic cancer or progressive ovarian cancer is disseminated to peritonea, prognosis after surgical excision is likely to fall short of expectations.
Therefore, an attempt is being made to develop gene therapy as a new method for treating cancer. The following gene therapies against cancer are being studied: (1) a method for inhibiting the growth of tumor cells by controlling oncogenes using antisense or ribozyme, or by introducing antioncogenes; (2) a method for introducing a metabolically toxic gene (suicide gene) into tumor cells to cause them to commit suicide: (3) a method for enhancing anti-tumor immunity by introducing genes; (4) a method for protecting bone marrow stem cells using multidrug-resistant genes for the purpose of improving the effect of chemotherapy; and the like.
As a method of (2) as listed above, a method which employs the thymidine kinase of herpes simplex virus as a suicide gene is known. For example, the thymidine kinase of herpes simplex virus is introduced into cancer cells, and thereafter, ganciclovir is administered. The ganciclovir is phosphorylated by the thymidine kinase of herpes simplex virus to be activated. The activated ganciclovir inhibits the DNA polymerase of cancer cells. Therefore, by introducing the thymidine kinase of herpes simplex virus into cancer cells, the growth of the cancer cells can be suppressed, and it is also possible that the cancer cells are completely destroyed.
Since herpes simplex virus is a pathogenic virus, wild-type HSV cannot be used for cancer therapy. Therefore, research is directed to the use of attenuated herpes simplex viruses for cancer therapy (WO96/39841).
Therefore, an attempt has been made to use gene therapy as a novel therapy for cancer. As an example of such a gene therapy, a metabolically toxic gene (suicide gene) is introduced into tumor cells which are caused to commit suicide. More specifically, a method using the thymidine kinase of herpes simplex virus as a suicide gene is known.
As described above, herpes virus, such as herpes simplex virus (e.g., herpes virus type 1 (HSV-1) capable of replication), may mediate the destruction of tumor cells. Therefore, the use of a genetically engineered HSV-1 virus vector capable of replication is studied in association with antitumor therapy.
As such a HSV-1 virus vector, a γ34.5-deficient strain which lacks the γ34.5 gene (γ34.5) and therefore has a reduced level of neurotoxicity has been used, so that a certain level of its antitumor effect was demonstrated. However, the γ34.5-deficient strain has not yet become practical.
The present inventors have concentrated on a gene encoding US2 of HSV-2 (hereinafter abbreviated as US2 gene) and a gene encoding US3 of HSV-2 (hereinafter abbreviated as US3 gene), and investigated the pathological roles of these genes using a US2-deficient mutant or a US3-deficient HSV gene recombinant. As a result, the present inventors revealed that neither the US2 nor US3 gene is necessarily essential for the replication of the respective viruses in cell culture, and the US3-deficient HSV gene recombinant is significantly attenuated (Nishiyama, Y., Yamada, Y., Kurachi, R., and Daikoku, T (1992), “Construction of a US3 lacZ insertion Mutant of herpes simplex virus type 2 and characterization of its phenotype in vitro and in vivo”, Virology 190, 256-268; Daikoku, T., Yamashita, Y., Tsurumi, T., Maeno, K., and Nishiyama, Y (1993), “Purification and biological characterization of the protein kinase encoded by the US3 gene of herpes simplex virus type 2”, Virology 197, 685-694; Jiang, Y-H., Yamada, H., Goshima, F., Daikoku T., Oshima, S., Wada, K., and Nishiyama, Y (1998), “Characterization of the herpes simplex virus type 2 (HSV-2) US2 gene product and a US2-deficient HSV-2 mutant”, J. Gen. Virol. 79, 2777-2784).
Previous research on genital herpes using murine models revealed that unlike infection with HSV-1 strain KOS, intravaginal infection with highly virulent HSV-2 strain 186 fails to induce increases in activated T cells within the vagina or a rapid increase of APC (antigen-presenting cell) in the early phase of infection (Inagaki-Ohara K, Daikoku T, Goshima F, Nishiyama Y, “Impaired induction of protective immunity by highly virulent herpes simplex virus type 2 in a murine model of genital herpes”, Arch Virol. 2000; 145(10): 1989-2002.).
Therefore, the objective of the present invention is to provide a characteristic-modified herpes virus construct, the use thereof, or a method using the same so as to treat or prevent diseases or disorders associated with herpes virus, or other diseases or disorders.